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A reflecting surface is represented by the equation `y = (2L)/(pi) sin ((pi x)/(L))`, where `0 le x le L`. A ray of light travelling horizontally becomes vertical after reflection with the surface. The co-ordinates of the point where this ray is incident is. A. `((L)/(4), (sqrt2L)/(pi))`B. `((L)/(3), (sqrt3L)/(pi))`C. `((3L)/(4), (sqrt2L)/(pi))`D. `((2L)/(3), (sqrt3L)/(pi))` |
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Answer» Correct Answer - B `((dy)/(dx))_("tangent") = 2 cos (pi x)/(L)` and tan `(90 + 45^(@)) = ((dy)/(dx))_("normal")` `rArr x = (L)/(3), y = (sqrt3L)/(pi)` |
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